Populations of frogs and other amphibians are declining at an average rate of 3.7 percent each year, according to a new U.S. Geological Survey study. Karen Bleier/AFP/Getty Images hide caption

itoggle caption Karen Bleier/AFP/Getty Images

For centuries, Russians believed putting a brown frog in their milk would keep it fresh. Now scientists are finding chemicals in the frog's slimy goo that inhibit the growth of bacteria and fungi. Stefan Arendt/Corbis hide caption

itoggle caption Stefan Arendt/Corbis